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-   -   Is GM Vortec 454 essentially the same thing as the 300-HP L29 7.4L? (https://www.offshoreonly.com/forums/general-q/298820-gm-vortec-454-essentially-same-thing-300-hp-l29-7-4l.html)

MILD THUNDER 06-26-2013 09:38 AM

Throw up a post in the wanted section here. Prob have one located by tonight.

28Eliminator 06-26-2013 09:39 AM


Originally Posted by MILD THUNDER (Post 3949350)
That'd work. Really not bad engines. A definite step up from the old peanut port 330 flat tappet engines. The cam in them is factory installed retarded like 7 degrees or something like that. I suppose if you were gonna do the carb, then maybe slap the 454 mag cam in it if you can find one cheap. They're 9:1, I actually think with the mag cam, intake and carb it be a pretty decent running engine!

I agree, I think it would be a good runner also. I think they were rated at 285hp, but that might be at the rear wheels. With a good intake and carb it should run good, but i'm not sure the cam change will make a lot of difference.

Budman II 06-26-2013 09:45 AM

Anyone think it will run at all with the 800 Holley on it, or will it fall on its face? I don't really care if it revs much past 4600 RPM - I just want to have the boat running for the remainder of the summer. I'll be getting the cold shoulder from the wife and kids if it's not running in time for our lake trip in July.

I also have a line on essentially the same engine in an early-90's Fountain. Guy bought the boat thinking it had 385 mags in it. One started knocking - bad wrist pin. Pulled it and found out it was an L29 out of a Suburban. Remaining engine was still running OK, but not sure how much use/abuse it has had. However, it is possible for me to hear this one run before buying it.

MILD THUNDER 06-26-2013 09:47 AM


Originally Posted by 28Eliminator (Post 3949382)
I agree, I think it would be a good runner also. I think they were rated at 285hp, but that might be at the rear wheels. With a good intake and carb it should run good, but i'm not sure the cam change will make a lot of difference.

I have one in my 97 Dually. Before that I had a 89 dually with the TBI peanut port headed engine. The vortec is a much nicer engine. actually will make some power past 3500rpm. The cam change might give it a little more rpm. I think the stock cam is done around 4400-4600. Not that i'd spin the stock internals more than about 5k.

Putting the mag cam in it, would be a pretty good comparison of the vortec head setup vs the GM rect port head setup. The compression is close to a 454 mag, slightly higher.

The truck L29 was rated at 290HP. The marine version 310HP. The marine setup had a different intake/injectors but same internals.

MILD THUNDER 06-26-2013 09:49 AM


Originally Posted by Budman II (Post 3949384)
Anyone think it will run at all with the 800 Holley on it, or will it fall on its face? I don't really care if it revs much past 4600 RPM - I just want to have the boat running for the remainder of the summer. I'll be getting the cold shoulder from the wife and kids if it's not running in time for our lake trip in July.

I also have a line on essentially the same engine in an early-90's Fountain. Guy bought the boat thinking it had 385 mags in it. One started knocking - bad wrist pin. Pulled it and found out it was an L29 out of a Suburban. Remaining engine was still running OK, but not sure how much use/abuse it has had. However, it is possible for me to hear this one run before buying it.

I don't see why it wouldn't. The quadrajets that came on the old 330's were 800cfm I believe.

28Eliminator 06-26-2013 09:52 AM

Budman II, I think it will run fine with a 800. It might be a little bigger than you need, but if it has vacuum secondaries it will only draw what it can.

Budman II 06-26-2013 09:54 AM


Originally Posted by MILD THUNDER (Post 3949388)
I don't see why it wouldn't. The quadrajets that came on the old 330's were 800cfm I believe.

Q-jets were 750 cfm, but since the secondaries were vacuum controlled, they were generally a little more forgiving.

MILD THUNDER 06-26-2013 10:03 AM

I have a engine masters issue here. They tested several carbs ranging from 650-950cfm on a 372ci small block with some good parts.

The highest HP AND torque was with the 950.

AVG HP/TQ from 2500-6000RPM.

600CFM Holley DP 380HP/428FT lbs
650CFM Demon 374HP/421FT lbs
750CFM Holley DP 383HP/430FT lbs
950CFM Holley DP 387HP/435FT lbs.

All carbs were mechanical secondary.

MILD THUNDER 06-26-2013 10:13 AM

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tpabayflyer 06-26-2013 10:32 AM

I built my L-29 up using the .510/.540 magnum cam and it runs awesome! It has a little more rumble at idle but has excellent torque at 3,000 an above. I bought the cam for less than $200 and got a new single row timing chain as well and it was pretty cheap. I did install larger valves and did some minor, basic port cleanup but I think the gains were very small from that. Use a nice air gap dual plane intake and throw that 800 carb on and enjoy the summer! TBF


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